Alright, Maya, hold up. You're asking for the *simplest* way, but you're already mixing up the problem. eBPF sniffing the network for patterns is one thing, but you asked if it's the right tool for catching credentials "before they hit the network."

If an agent is just assembling a string to send, that's in userspace memory. Your eBPF hook would need to trace the agent's own functions, maybe `write()` or `send()`. That's a different beast than just scanning packets. By the time it's in a packet, it's already exfiltrating.

For a dead-simple network-only test, try `bpftrace`. One-liner to watch for 'sk_' patterns in outbound TCP data. But you'll drown in false positives from encrypted traffic. It's a fun demo, but practically useless against any modern agent that uses TLS. Good luck spotting that API key in a TLS 1.3 stream.

For the specific scenario you outlined, starting with a network eBPF tool like bpftrace is indeed the simplest path for a beginner experiment, but user380's caveat about TLS is critical. You'll see nothing but encrypted blobs.

If you want to follow that path anyway, install bpftrace. A basic script to attach to `kprobe:tcp_sendmsg` and scan the data buffer for a simple pattern, like a 20+ character alphanumeric string, would be:

```
#!/usr/bin/env bpftrace
kprobe:tcp_sendmsg
{
$sk = (struct sock *)arg0;
$size = arg2;
if ($size > 20) {
$data = buf($sk->sk_snd_buf, $size);
if (str($data, "sk_") != 0) {
printf("Potential API key sent by PID %d: %sn", pid, str($data, 0, 64));
}
}
}
```

You'd see alerts in the terminal where you run bpftrace. This is purely illustrative; the real value for pre-network interception is in tracing userspace library calls like `SSL_write`, which requires uprobe support and symbol resolution, moving you far from "absolute simplest." For a meaningful experiment, I'd suggest first using this to monitor a plaintext HTTP POST from a test curl command to see the flow.

That script has a fundamental structural error that will prevent it from running. `sk_snd_buf` is not a member you can access like that from the `struct sock` in a kprobe context for this purpose. The `buf()` function expects a pointer to the data buffer itself, not a socket struct member. The correct approach would be to use `arg1` as the `struct msghdr *msg`, then traverse `msg->msg_iter` to get to the data, which is not beginner territory at all.

user258's final suggestion is the only viable part: use it to monitor a plaintext test. But the provided code won't compile. For a true minimal example that actually functions to illustrate the data flow, you'd need a simpler, working pattern. Even then, without uprobes on the agent's memory or SSL library, you're just watching the encrypted pipe, which as noted, is useless for the stated goal.

If the experiment is about understanding eBPF mechanics, start with `bpftrace -e 'kprobe:tcp_sendmsg { printf("PID %d sending %d bytesn", pid, arg2); }'`. If it's about catching credentials, you've already lost if you're only looking at the network layer with this technique.